Manufacture of structural members and components

ABSTRACT

An identical pair of bar-like structural components of novel shape may be produced from a straight length of timber of rectangular cross section by severing it lengthwise. The length of material may be mounted on a carriage arranged to feed the material axially forward in a straight line past a band saw, such carriage being capable of rocking about the axis which passes through the geometric center of the cross-section of the material, and so rocking he length relative to the saw blade about such axis that the saw divides the top and bottom surfaces into the two components, having complementary opposed convex and concave edges. The two resulting components are then secured together as by gluing to produce a composite beam the strength of which is greatly in excess of the strength of the original unsevered length of timber. Composite beams may be produced by assembling four identical components in pairs back to back. Components of similar shape may be formed in other materials by moulding so as to possess comparable strength characteristics, according to the nature of the material. A panel may be stiffened by securing to its under side a number of components so formed.

O United States Patent 1151 3,654,741 MacDonell [451 Apr. 11, 1972 54MANUFACTURE OF STRUCTURAL 571,021 2/1959 Canada ..52/730 MEMBERS ANDCOMPONENTS Istvglitzerland [72] Inventor: Murray Macnoneu, g England y[73] Assignee: Montague L. Meyer Limited, London, En- Primary Abbott l dAssistant ExaminerLesl1e A. Braun Filed. Mar 24 1970 Attorney-Bacon andThomas [21] Appl. No.: 22,360 ABSTRACT An identical pair of bar-likestructural components of novel [30] F i A li ti P io it Dat shape may beproduced groin a straigllit lerl11gth oiirtlilmber or:

. rectangu ar cross section ysevering it engt wise. e engt Mar. 27, 1969Great Britain 16,093/69 of material may be mounted on a carriagearranged to feed the material axially forward in a straight line past aband saw, such 2% P' carriage being capable of rocking about the axiswhich passes l 732 734 through the geometric center of the cross-sectionof the l 1 o material, and so rocking he length relative to the sawblade about such axis that the saw divides the top and bottom sur- [56]References cued faces into the two components, having complementary op-UNITED STATES PATENTS posed convex and concave edges. The two resultingcomponents are then secured together as by gluing to produce a 1,460,0906/1923 Baehr composite beam the Strength of which i g y in excess of13322 4/1938 Henqench "52/734 the strength of the original unseveredlength of timber. Com- 2382208 8/1945 q i posite beams may be producedby assembling four identical 3396504 8/ g i 4 components in pairs backto back. Components of similar 3 1 3 "52/608 shape may be formed inother materials by moulding so as to 3 95369 aroc e possess comparablestrength characteristics, according to the FOREIGN PATENTS ORAPPLICATIQNS nature of the material. A panel may be stiffened bysecuring to 24 405 6/l901 S t2 1 d 52/730 its under s1de a number ofcomponents so formed.

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saw 10 0F 12 IN VE' N TOR Muemv MHCOONELL Zzm/AW ?ATENTEDAPR I I I972SHEET 11 0F 12 IN VEN TOR Mumm Mama L MANUFACTURE OF STRUCTURAL MEMBERSAND COMPONENTS This invention relates to structural members in thenature of beams, and to methods for producing them economically.

It is recognized that, in the majority of instances, the use of a solidbeam of constant cross section involves uneconomical use of material.This applies particularly to timber beams. In order to provide adequateresistance to the anticipated loading on a beam of constant crosssection extending between supports at each of its ends, a section has tobe chosen which will resist the maximum bending moment.

Generally speaking, for a beam supported at its ends and carrying auniformly distributed load, the maximum bending moment occurs at theends of the beam. It can be shown by a mathematical calculation that abeam of constant depth requires to have maximum cross sectional width atits upper and lower surfaces, to resist bending moments, and to havemaximum width at its center of depth, to resist shear. A beam involvingeconomical use of material will therefore require, maximum width at theupper and lower surfaces and near the center of its span and maximumwidth at the center of depth at and near its ends.

The present invention aims to provide a solid beam having thesecharacteristics, and made either as a composite assembly from similarlyshaped components, or made by casting or moulding. It further aims toprovide an economic method of making such a beam and components, bycutting from solid lengths of material (normally timber), and of makingmoulds for the manufacture of such beams when they are to be formed bycasting.

The invention is based on, and developed from, the discovery that it ispossible to cut a normal rectangular section timber beam lengthwise, soas to sever it into two complementary and substantially identical halvesof unusual shape, such halves constituting bar-like members which, whenfirmly assembled together, will provide a composite beam of the samelength but with greatly improved bending strength.

According to the present invention there is provided a barlike memberfor structural purposes, having a top and bottom surface, two endsurfaces and two side surfaces, and in which the top and bottom surfacesare flat surfaces at least one of which lies in a (notional) horizontalplane and both of which lie in planes perpendicular to the (notional)vertical plane; one of those flat surfaces progressively increasing inwidth from both ends to a maximum at substantially the mid-position ofthe members length so that, in plan view, that surface is substantiallysymmetrical about that mid-position and has a substantially convex edge;the other of those flat surfaces progressively decreasing in width fromboth ends to a minimum at substantially the mid-position of the memberslength so that, in plan view, that surface is likewise substantiallysymmetrical about that mid-position but has a substantially concave edgelocated at the same side of the member as the said convex edge; whilethe side surface which is bounded by edges of the two ends and by theconvex and concave edges (herein called the principal side surface)contains a straight line (herein called the basic line") running fromend to end of the member and located substantially mid-way between theconvex and concave edges, the principal side surface also being soshaped that any line perpendicular to the basic line and running fromthe convex edge to the concave edge is straight.

Preferably, the curvature of the convex edge matches, and iscomplementary to the curvature of the concave edge. In most cases, thetop and bottom surfaces will lie in planes which are parallel in bothdirections, though in some instances those surfaces may lie inplaneswhich are parallel in one direction and convergent/divergent in theother direction. In cases where members are to be assembled back to back(as hereinafter described the side surface opposite to the principalside surface is a flat surface, which lies in the plane perpendicular tothe planes of the top and bottom surfaces.

The invention includes a method of making a pair of barlike members asset forth above, by severing with a longitudinal cut, a length of solidmaterial, such as timber, of substantially constant cross section, andwhich has flat top and bottom surfaces, in such a manner as to divide itinto two such members or components which, if left undisturbed havetheir respective interfitting principal side surfaces opposed, andmeeting at a notional interface resulting from the movement of the lineof cut through the length of solid material.

Various embodiments of the invention will now be described by way ofexample only, and with reference to the accompanying illustrativedrawings. It is pointed out that in all the Figures the lengthwisedimensions of the members of components, and of the beams formed fromsuch components, have been deliberately shortened relative to the otherdimensions, in order to illustrate curvature more clearly.

IN THESE DRAWINGS FIG. 1 is an isometric view of a typical member inaccordance with the invention, while FIGS. 1A and 1B are respectively anend elevation and a mid-point section of the same member, viewed fromthe left of FIG. 1.

FIG. 2 is an isometric view of a rectangular section showing the line ofcut required to produce members in accordance with FIG. 1.

FIG. 3 is an isometric view of an assembly of two members in accordancewith FIG. 1 to produce a composite beam.

FIG. 3A is an end view of the composite beam of FIG. 3, while FIGS. 3Band 3C are sections at its quarter points and mid-points respectively.

FIG. 4 is an isometric view of a composite beam made by assembling twocomposite beams of the kind illustrated in FIG. 3 in a back to backposition.

FIGS. 4A, 4B and 4C are respectively an end view, quarter point sectionand mid-point section of the composite beam of FIG. 4.

FIG. 5 is an isometric view which illustrates a method of cutting alength of material of which the cross section is a parallelogram.

FIG. 6 is an isometric view which shows a composite beam made byassembling the two members produced from FIG. 5, while FIGS. 6A and 68respectively show the end view and center section of the composite beamof FIG. 6.

FIG. 7 is an isometric view which shows a method of cutting a length ofmaterial of which the cross section is a parallelogram but angled in theopposite sense to that of FIG. 5.

FIG. 8 is an isometric view which shows a composite beam made byassembling the two members produced from FIG. 7, while FIGS. 8A and 88respectively show the end view and center section of the composite beamof FIG. 8.

FIGS. 9 and 9A are isometric views which show how a length of materialof considerable cross sectional depth in relation to its cross sectionalwidth, may first be divided into two generally wedge shaped members, bya horizontal cut, and then sub-divided by the method of the invention.

FIG. 10 is an isometric view which shows a composite beam produced fromtwo of the members of FIG. 9.

FIG. 11 is an isometric view which shows yet another way of severing alength of material.

FIG. 12 is an isometric view which shows a composite beam made byassembling the two members produced from FIG. 11.

FIG. 13 is an isometric view of an assembly of two members in accordancewith FIG. 1 to produce one side of a mould.

FIGS. 13A and 13B are respectively an end view and mid sectional view ofa mould formed by erecting two members according to FIG. 13 oppositeeach other.

FIG. 14 shows a stiffened panel, utilising members in accordance withFIG. 1 as stiffeners.

FIG. 15 is an isometric view which shows how the method of the inventionmay be applied to sever, in its longitudinal direction, a length ofmaterial which initially has two outer side surfaces similar in shape tothe principal side surface previously defined.

FIG. 17 is an end view which shows how the method of the I invention maybe applied to sever a length of material having parallel top and bottomfaces, but otherwise barrel shaped in cross section.

FIG. 18 shows an end view of a composite beam formed by assembling twomembers formed from FIG. 17.

FIGS. 19 to 22 are diagrams which illustrate comparative calculations ofmaximum second moment of area of the cross section at mid-span of beamsof varying section.

Referring to FIGS. 1, 1A and 1B, which illustrate the basic conceptunderlying the invention, the bar-like member shown in perspective inFIG. 1 has a top surface 1 and a bottom surface 2, both of which areflat surfaces, and in this example, lie in parallel planes. These planesare perpendicular to the vertical plane of the side 4 of the member. Thetwo ends 3 lie in parallel planes perpendicular to the surfaces 1, 2 and4. The top surface lgradually increases in width in a fair curve fromits two ends 3 to a maximum at substantially the mid position of themember, so that in plan view that surface is substantially symmetricalabout that mid-position, and has a substantially convex edge la. Thebottom surface 2 progressively decreases in width in a fair curve fromboth ends 3, to a minimum at substantially the mid-position of themember, so that in plan view that surface is also substantiallysymmetrical about that mid position, but has a substantially concaveedge 2a.

In this embodiment, the curves at the edges of the top and bottomsurfaces are of identical curvature but reversed, one being concave andthe other convex, and the end edges 3a of the top surface 1 are equal inwidth to each other and are also equal to the narrowest width of thebottom surface 2, while the end edges 3b of the bottom surface 2 arelikewise equal in width to each other and are also equal to the widestwidth of the top surface 1. As a result of this arrangement, the basicline 6 which is shown in chain dots in FIG. 1, lies at the mid heightposition of the curved surface of principal side surface of the member.

FIG. 2 shows how a length of material, whose total width is the sum ofthe edges 3a and 3b, can be divided by a saw cut 7 running lengthwise ofthe member, so as to produce two members of identical shape each inaccordance with the shape shown in FIG. 1, and lying side-by-side withthe surface 1 of the one member which has a convexly curved edgecontiguous with the surface 2 of the other member which has a concavelycurved edge and vice versa.

FIG. 3 shows a composite beam formed by assembling two members A and B,made by severing a length of material as described in relation to FIG.2, and assembling the resulting components so that the surfaces havingconcave edges are contiguous. The end, quarter point and center sectionsof this beam are respectively illustrated in FIGS. 3A, 3B and 3C.

It will be appreciated that by comparison with the bending strength andstiffness of a rectangular beam of the total section of the member ofFIG. 2 from which the two members A and B are formed, the bendingstrength and stiffness of the composite beam of FIG. 3 is veryconsiderably increased without loss of material.

To produce an even stronger structure, two beam assemblies made inaccordance with FIG. 3 may be secured back-toback as illustrated in FIG.4, in which four members A, A, B and B, are all secured together toproduce a composite beam having approximately twice the bending strengthand stiffness of the beam illustrated in FIG. 3. The end, quarter pointand center sections of this beam are illustrated in FIGS. 4A, 4B and 4Crespectively.

FIG. 5 shows the effect of applying the method of the invention to alength of material of which the cross section is a parallelogram, toproduce two identical members C and C which are assembled as shown inFIG. 6, to form a composite beam generally similar to the beam of FIG.3, but having and end shape as shown in FIG. 6A and a center section asshown in FIG. 6B.

FIG. 7 shows the affect of applying the method of the invention to alength of material of which the cross section is a parallelogram, angledin the opposite sense to, but cut in the same manner as, the crosssection of FIG. 5, to produce two identical members D and D which areassembled as shown in FIG. 8 to forrnv a composite beam generallysimilar to the beams of FIGS. 2 and 6, but having an end shape as shownin FIG. 8A and a center section as shown in FIG. 8B.

FIGS. 9 and 9A show a variant in which a length of material, of whichthe rectangular cross section is deep in relation to its width, is firstdivided into two identical wedge-like members by a straight cut on theline 8. These two members are subsequently sub-divided by the method ofthe invention so as to produce four identical members E, E and F, F,which may be assembled as shown in FIG. 10, E with F or E with F toproduce a composite beam of varying bending strength along its length.

FIG. 11 shows yet another method of cutting a length of material ofrectangular cross section, in which the saw cut 9 is initially in thevertical plane. This produces two identical members G, G which may beassembled as shown in FIG. 12 to produce a composite beam.

FIG. 13 shows a method of assembling two members produced as describedin relation to FIG. 2, but so that the surfaces having convex edges aresecured together to overlie one another. A member of this kind may beused as a mould, the conjoint principal side surfaces together forming amoulding surface. For example two such members of FIG. 13 may beerected, as illustrated in FIGS. 13A and 13B, opposite to each other toform a mould, FIG. 13A being a view of the end of the mould and FIG. 138being a section at its mid-position. Material cast into the spacebetween the mould, will result in a beam of the same configuration asthat shown in FIG. 4.

FIG. 14 shows another use for the member of FIG. 1. In this example fourmembers 10, each shaped as shown in FIG. 1, are secured to the undersideof the sheet 11 to form a stiffened panel.

The invention is not limited to manufacture from lengths of materialwhich are straight sided in a longitudinal direction.

FIG. 15 illustrates an example generally similar TO FIG. 5, but in whichthe edges 12 of the length of material are curved as can be seen inrelation to the dashed lines on the Figure. A length of material of thisshape when cut in accordance with the method of the invention into twoidentical members H and H, can be assembled as shown in FIG. 16 to forma composite beam, of which the end view and center section arerespectively shown in FIGS. 16A and 16B.

Likewise, the invention is not limited to manufacture from lengths ofmaterial which are straight sided in a vertical direction.

FIGS. 17 and 18 (which are end views) illustrate an example similar toFIGS. 2 and 3, in which the length of material in cross section hasparallel flat top and bottom surfaces 13 and barrel shaped side surfaces14. When severed in accordance with the method of the invention the twoidentical members produced may be assembled as shown in FIG. 18, withthe conjoint principal side surface 15 of similar shape to the principalside surface of the example of FIG. 3. The opposite conjoint surface14.14 to the conjoint principal side surface, has a double curvatureresulting from the juxtaposition of the two curved sides 14 of the twocomponents.

It will be appreciated that the invention is principally applicable tomanufacture from timber, and that the composite beams are preferablyproduced by using suitable adhesives between the adjacent surfaces, withor without additional fixings such as pins or screws.

Normally, rectangular section lengths of material will be used, andthese may be severed as described with relation to the various examples,by mounting them on a carriage, arranged to feed each length axiallyforward in a straight line past a band saw, the carriage being capableof rocking the material about the axis which passes through thegeometric center of the cross section of the material. The carriage isthen arranged to rock as necessary relative to the saw blade, about thataxis, so that the saw will divide the top and bottom surfaces of thematerial into shapes having complementary opposed convex and concaveedges. In some cases the saw may rock relative to the carriage and/orthe saw may be fed forwards through the material being cut.

FIGS. 19 to 23 are diagrams which relate to timber beams and illustratedthe comparative second moments of area at mid-span of various typicalcross sections of beam. In the diagrams the expression 1" represents thesecond moment of area" of the beam, which may be used with other data tocalculate strength and to give an approximate indication of stiffness.

The calculations for arriving at 1" have not been given in detail, asthey are well known to structural engineers.

In FIG. 19 there is shown a rectangular cross section of a timber beamhaving a width w of 3% of an inch and a notional depth d. In thisinstance the stiffness l" equals 0.323 d.

FIG. 20 shows a beam made by severing the section of FIG. 19 in thevertical plane into two equal halves of which the width W is constantthroughout and may be assumed to be fractionally less than half thewidth of the section from which it was cut (allowing for the loss ofmaterial due to the saw cut). This width w may be assumed as 1% inch.The total depth of this composite beam, which is glued together at thecenter, is 2d. In this instance 1"= 1.25 d

FIG. 21 shows a section at its mid-position of a composite beam inaccordance with FIG. 3. This section in fact represents the sectionshown in FIG. 3C. The section has a depth 2d and a width W2 at itsextreme top and bottom surfaces and a width y at its half height. Inthis case I zP/6 (y 3W2).

It will be appreciated that since the section has been cut from thebasic section of FIG. 19 and allowing for a width of saw cut of /s inchthen (w 3% inch. If the width y at half height is taken as inch and thewidth W2 at the top and bottom surfaces is taken as 3 inch then I 1.625fi.

FIG. 22 shows curves which illustrate the varying I values of beamshaving cross sections similar to those of FIGS. 19 to 21, assuming thebasic section of FIG. 19 to have the dimensions shown in the horizontalordinates of the graph. The vertical ordinates represent the I value.

The section of FIG. 21 shows I value increase over the basic section ofFIG. 19 of 403 percent, and an I value increase over the compositionsection of FIG. 20 of 30 percent.

It is to be understood that, in the case of members cut from timber, thetimber may either be solid or built up from glued timber laminates.

I claim:

1. An elongated structural member having a top and a bottom surface, twoend surfaces and two side surfaces, and in which said top and bottomsurfaces are flat surfaces at least one of which lies in a horizontalplane and both of which lie in planes perpendicular to a vertical planeextending longitudinally of said member; one of said flat surfacesprogressively increasing in width from both its ends to a maximum atsubstantially the mid-position of said member's length so that, in planview, such first flat surface is substantially symmetrical about suchmid-position and has a substantially convex curved edge on one side ofsaid member; the other of said fiat surfaces progressively decreasing inwidth from both its ends to a minimum at substantially the mid-positionof said member's length so that, in plan view, such second flat surfaceis likewise substantially symmetrical about such mid-position but has asubstantially concave curved edge located at the same side of saidmember as said convex edge; the side surface between said curved edgescontaining a straight longitudinal line midway between said curvededges, said side surface being so shaped that any line perpendicular tosaid straight line and running from said convex edge to said concaveedge is straight.

2. A member as claimed in claim 1, in which the curvature of said convexedge matches, and is complementary to, the curvature of said concaveedge.

3. A member as claimed in claim 1, in which said top and bottom surfaceslie in parallel planes. I

4. A member as claimed in claim 1, In which said top and bottom surfaceslie in longitudinally convergent planes.

5. A member in accordance with claim 1, in which the other side surface,opposite to said side surface, is a flat surface, which lies in a planeperpendicular to the planes of said top and bottom surfaces.

6. A structural assembly comprising two substantially identicalassemblies as claimed in claim 5, assembled and secured together so thattheir respective conjoint flat side surfaces substantially coincide.

7. A structural member in the nature of a beam, comprising an assemblyof two substantially identical components according to claim 1, the flatsurface of each member having said concave edge being firmly secured tothe corresponding surface of the other member, so that such surfacessubstantially coincide.

8. A structural assembly comprising two substantially identicalassemblies as claimed in claim 7, assembled and secured together so thattheir respective conjoint flat side surfaces substantially coincide.

9. A member having the external shape and surface configuration of themember of claim 7, but formed integrally by molding or casting.

10. A member comprising an assembly of two substantially identicalcomponents according to claim 1, the flat surface of each member havingsaid convex edge being firmly secured to the corresponding surface ofthe other member, so that such surfaces substantially coincide.

11. A member according to claim 1 made from a length of timber.

12. A stiffened panel comprising a flat sheet of material reinforced bya bar-like member as claimed in claim I.

13. A method of making a pair of structural members which compriseslongitudinally severing a length of solid material of substantiallyconstant cross section, which has flat top and bottom surfaces, bycutting therethrough along a line of cut extending from said top to saidbottom surface, said line of out being tilted relative to said surfacesat a predetermined angle at one end of said material, relatively tiltingsaid material and line of cut as said line is moved longitudinally sothat the line of cut progressively tilts relative to said surfaces totilt in the opposite direction at the midlength of said material, thenback to said predetermined angle at the other end of said material.

753 3 UNITED STATES PATENT OFFICE QE'HFICATE 0F CORRECTION 3, 654,741 Dd April 11, 1972 Patent No.

Inventor 5;) Murray Macdonell It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

In the specification, column 5, line 30,

I d /6 (y 3W should read:

Signed and sealed this 12th day of September 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

1. An elongated structural member having a top and a bottom surface, twoend surfaces and two side surfaces, and in which said top and bottomsurfaces are flat surfaces at least one of which lies in a horizontalplane and both of which lie in planes perpendicular to a vertical planeextending longitudinally of said member; one of said flat surfacesprogressively increasing in width from both its ends to a maximum atsubstantially the mid-position of said member''s length so that, in planview, such first flat surface is substantially symmetrical about suchmidposition and has a substantially convex curved edge on one side ofsaid member; the other of said flat surfaces progressively decreasing inwidth from both its ends to a minimum at substantially the mid-positionof said member''s length so that, in plan view, such second flat surfaceis likewise substantially symmetrical about such mid-position but has asubstantially concave curved edge located at the same side of saidmember as said convex edge; the side surface between said curved edgescontaining a straight longitudinal line midway between said curvededges, said side surface being so shaped that any line perpendicular tosaid straight line and running from said convex edge to said concaveedge is straight.
 2. A member as claimed in claim 1, in which thecurvature of said convex edge matches, and is complementary to, thecurvature of said concave edge.
 3. A member as claimed in claim 1, inwhich said top and bottom surfaces lie in parallel planes.
 4. A memberas claimed in claim 1, in which said top and bottom surfaces lie inlongitudinally convergent planes.
 5. A member in accordance with claim1, in which the other side surface, opposite to said side surface, is aflat surface, which lies in a plane perpendicular to the planes of saidtop and bottom surfaces.
 6. A structural assembly comprising twosubstantially identical assemblies as claimed in claim 5, assembled andsecured together so that their respective conjoint flat side surfacessubstantially coincide.
 7. A structural member in the nature of a beam,comprising an assembly of two substantially identical componentsaccording to claim 1, the flat surface of each member having saidconcave edge being firmly secured to the corresponding surface of theother member, so that such surfaces substantially coincide.
 8. Astructural Assembly comprising two substantially identical assemblies asclaimed in claim 7, assembled and secured together so that theirrespective conjoint flat side surfaces substantially coincide.
 9. Amember having the external shape and surface configuration of the memberof claim 7, but formed integrally by molding or casting.
 10. A membercomprising an assembly of two substantially identical componentsaccording to claim 1, the flat surface of each member having said convexedge being firmly secured to the corresponding surface of the othermember, so that such surfaces substantially coincide.
 11. A memberaccording to claim 1 made from a length of timber.
 12. A stiffened panelcomprising a flat sheet of material reinforced by a bar-like member asclaimed in claim
 1. 13. A method of making a pair of structural memberswhich comprises longitudinally severing a length of solid material ofsubstantially constant cross section, which has flat top and bottomsurfaces, by cutting therethrough along a line of cut extending fromsaid top to said bottom surface, said line of cut being tilted relativeto said surfaces at a predetermined angle at one end of said material,relatively tilting said material and line of cut as said line is movedlongitudinally so that the line of cut progressively tilts relative tosaid surfaces to tilt in the opposite direction at the midlength of saidmaterial, then back to said predetermined angle at the other end of saidmaterial.